The invention relates to an optical polarization regulator having a wave-guide structure for converting the polarization state of an optical beam passed through and comprising devices for adjusting the coupling constants K of the TE and TM modes of the optical beam and for adjusting the difference .DELTA..beta. of the propagation constants .beta..sub.TE and .beta..sub.TM of these modes.
Such arrangements known from German Offenlegungsschrift No. 3600458 serve to specifically change the polarization state of an optical beam. More particularly, linearly polarized light can be converted into elliptically polarized light having a given polarization. Preferably, such elements in the form of strip shapes wave-guides are required for heterodyne reception in the telecommunication technique. Two optical beams, whose frequencies differ from each other by an intermediate frequency, must be superimposed with their states of polarization as equal to each other as possible. The same applies to uses in which beams of the same frequency (intermediate frequency zero) are to be super-imposed. Not only is it required for the quotients of the TM and TE modes guided in orthogonal planes to be equal for both beams, but also the respective phase differences of the two modes have to be equal. In general, this can be achieved only by a regulation of the state of polarization of one of the two beams, for example of the local oscillator beam, which is to be adapted to the state of polarization varying with time of a beam incoming through an optical lead. Without readjustment, fluctuations of the intensity of the intermediate frequency signal would be obtained (compare also Electronic Letters, 1985, Vol. 21, p. 787-788).
In the known monolithic element of the kind mentioned in the opening paragraph, an electrooptical element, in which on the one hand K and on the other hand .DELTA..beta. are individually adjustable through different electrode systems having a complicated construction and applied to an electrical voltage, serves as wave-guide structure.